Although tourism is now Nevada's largest employer, the state was born from a mining boom in the 1860s, inspired by the discovery of a rich vein of silver ore christened the Comstock Lode.

Extraction still plays a signficant role in shaping the state's landscape and economy: the Nevada Bureau of Mines and Geology lists 29 gold and silver mines in its 2010 Mineral Industry Census, alongside claims that the state "continues to be in the midst of the biggest gold boom in U.S. history," producing up to eight times as much over the past thirty years as California did during its fabled Gold Rush.

Mine tour photographs by Nicola Twilley.

To get a glimpse of the state's subterranean origins, Venue visited Chollar Mine in Virginia City, which, between 1859 and 1942, yielded enough silver (and some gold) to rank as the third most productive mine on the Comstock. Curiously enough, it's now offered for sale, along with some mineral rights, although our guide assured us that it's much more viable as a tour business than as a working mine, given the flooding in the lower levels, the effort required to retrieve the remaining ore, and the not-insignificant cost of all the impact studies and permits needed to start a mining operation in Nevada today.

Gorgeous U.S. Geological Survey maps of the shafts and tunnels of the Comstock mines, published in 1881. The different colors used indicate each separate hundred feet of depth. From the David Rumsey collection in the Harvard University digital map library.

The Comstock Lode is legendary not just for the mineral wealth it yielded (an inflation-adjusted $400 million in silver per year, plus another $270 million in gold, at peak production in 1877), but for its role as a catalyst for extraction technology innovation.

As our guide explained, one of the major challenges faced by the miners was an ongoing battle against flooding from below by geothermal waters. When the Chollar Mine teamed up with neighboring mines to sink a new shaft to 3250 ft., they had to pump out 5 million gallons of water per day, as well as construct a special underground cooling chamber by lowering in big blocks of ice and buckets of ice water. Workers would spend 15 or 20 minutes working in the heat, and 15 or 20 minutes recovering in the cooling chamber, back and forth throughout their eight-hour shift.

The odd-looking structure to the right-hand side of the photograph is the head of the Combination Shaft, the deepest ever sunk on the Comstock, and so-called because it was a joint effort between the Chollar, Potosi, Hale & Corcross, and Savage mines.

In response, a 30-year-old German immigrant called Adolph Sutro proposed a wildly ambitious solution — drilling a 4-mile tunnel into the mountain that would use gravity to drain its mines from below, while simultaneously allowing equipment and ore to be shipped in and out at valley level rather than lowered and hauled up and down the mine shafts.

Work began on the Sutro Tunnel in 1869 and it opened in 1878 — but, by then, the Comstock had passed peak production, and improved ventilation and pump technology had already delivered many of the tunnel's proposed benefits. Sutro unloaded his own shares as soon as the tunnel was completed, and while his stockholders lost millions, he moved to San Francisco and became mayor.

The Sutro Tunnel has caved in in places now, and its entrance is off-limits, on private land. It is, nonetheless, a remarkable engineering landmark, and the direct forerunner of the large access and drainage tunnels still used by mines today.

Our guide told us this story while we stood 100 ft. underground in a stope — an auditorium-like hollow that had been mined out. Shored up tunnels and shafts led to more stopes, all around and beneath us — some as big as skyscrapers. And, in the second of the Comstock's engineering marvels, all of these underground voids are filled with cubes of heavy girders, arranged in regular grids like a wooden honeycomb inside the earth.

According to a 1912 history of Nevada, this "square-set" timbering system was invented by another German, Philipp Desdeheimer, as a modular solution that could be extended in any direction, "so as to fill in any ore-chamber as fast as the ore is taken out."

The unit in itself lies within the scope of a man's arms, but, built up in a series, it filled the vacant spaces left by the removal of the Con Virginia bonanza, hundreds of feet in height, in width, and in length.

The resulting lattice-work of notched timbers, held in place by the pressure of the rock all around them, looks uncannily like the skeleton of a skyscraper, stripped in order to construct its mirror image above ground.

Indeed, as the miners followed the vein of silver further into Mt. Davidson, more than 100 square miles of old growth pines around Lake Tahoe were clear-cut, with the forest brought underground to replace the minerals. Logging, our guide told us, quickly became the second biggest industry in Nevada, as the territory's newcomers rushed to rearrange its resources.

This gridded timber superstructure, stretching for miles underground, as the rocks whose place it took were transmuted into coin, forms a sort of forgotten Continuous Monument of extraction — a ghost forest built underground, in search of silver.

Thanks to Ronald James, the Nevada State Historic Preservation Officer, for the suggestion. If you think of any sites or people that Venue should visit, please let us know!